1/ The most disastrous earthquake in Japan, which occurred in 1923 killed about 150,000 people.

2/ The planet which is closest to the Earth is Venus.

3/ The animal which was closen to be the logo of Sea Games 2003 is the buffalo.

4/ The explorer who discovered America was Christopher Columbus.

5/ Pompeii was completely destroyed in AD 79 by an eruption of Mount Vesuvius.

6/ It snowed in Lang Son in the winter of 2002.

7/ Typhoon, hurricane, and cyclone are different words for the same matural disaster.

8/ They saw a lot of interesting buildings about their sight seeing trip.

9/ He was thought breaking the window last week.

10/ Everybody loves him because of his politeness.

1/ \(\left\{{}\begin{matrix}7x-3y=5\\\dfrac{x}{2}+\dfrac{y}{3}=2\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}7x-3y=5\\\dfrac{1}{2}x+\dfrac{1}{3}y=2\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{7}{3}x-y=\dfrac{5}{3}\\\dfrac{3}{2}x+y=6\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{23}{6}x=\dfrac{23}{3}\\7x-3y=5\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=3\end{matrix}\right.\)

Vậy hệ phương trình có nghiệm duy nhất \(\left(x;y\right)=\left(2;3\right)\)

2/ \(\left\{{}\begin{matrix}3x+y=3\\2x-y=7\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}5x=10\\3x+y=3\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=-3\end{matrix}\right.\)

Vậy hệ phương trình có nghiệm duy nhất \(\left(x;y\right)=\left(2;-3\right)\)

3/ \(\left\{{}\begin{matrix}2x+y=5\\3x-2y=11\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}4x+2y=10\\3x-2y=11\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}7x=21\\2x+y=5\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=3\\y=-1\end{matrix}\right.\)

Vậy hệ phương trình có nghiệm duy nhất \(\left(x;y\right)=\left(3;-1\right)\)

Giải:

Gọi chiều dài khu vườn hình chữ nhật là x (m: x >4)

Gọi chiều rộng khu vườn hình chữ nhật là y (m: x >y >0)

Diện tích khu vườn hình chữ nhật là x.y \(\left(m^2\right)\)

Nếu giảm chiều dài đi 4m, tăng chiều rộng lên 4m thì diện tích của khu vườn tăng thêm 32\(m^2\) nên ta có phương trình:

\(\left(x-4\right).\left(y+4\right)=xy+32\)

\(\Leftrightarrow xy+4x-4y-16=xy+32\)

\(\Leftrightarrow4x-4y=48\)

\(\Leftrightarrow4\left(x-y\right)=48\)

\(\Leftrightarrow x-y=12\) (1)

Nếu giảm chiều dài đi 4m, tăng chiều rộng lên 2m thì diện tích giảm 88\(m^2\) nên ta có phương trình:

\(\left(x-4\right).\left(y+2\right)=xy-88\)

\(\Leftrightarrow xy+2x-4y-8=xy-88\)

\(\Leftrightarrow2x-4y=-80\)

\(\Leftrightarrow2\left(x-2y\right)=-80\)

\(\Leftrightarrow x-2y=-40\) (2)

Từ (1) và (2) ta có hệ phương trình:

\(\left\{{}\begin{matrix}x-y=12\\x-2y=-40\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=52\\x-y=12\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}y=52\left(TMĐK\right)\\x=64\left(TMĐK\right)\end{matrix}\right.\)

Vậy chiều dài khu vườn hình chữ nhật là 64m

chiều rộng khu vườn hình chữ nhật là 52m

diện tích khu vườn khu vườn hình chữ nhật là 64.52=3328 \(\left(m^2\right)\)

Δ ABC cân tại A \(\left(\widehat{A}=90^o\right)\). Vẽ đường tròn đường kính AB cắt \(\stackrel\frown{BC}\) tại D, cắt \(\stackrel\frown{AC}\) tại E. Chứng minh:

a) \(\Delta DBE\) cân

b) \(\widehat{CBE}=\dfrac{1}{2}\widehat{BAC}\)

The company's director lacks lead skill

The company's director lacks (lead) skill

Đề bài: chuyển các động từ sau sang quá khứ

1, learn\(\rightarrow\) learnt/ learned

2, present \(\rightarrow\) presented

3,be \(\rightarrow\) was/ were

4, can \(\rightarrow\) could

5,say \(\rightarrow\) said

6, speak \(\rightarrow\) spoke

7, sing \(\rightarrow\) sang

8, dance \(\rightarrow\) danced

9, know \(\rightarrow\) knew

10, spell \(\rightarrow\) spelt/ spelled

1) The teacher is wearing a blue jacket. He teaches us mathematics.

--> The teacher who teaches us mathematics is wearing a blue jacket.

2) The garden is watered every morning. It is full of flowers.

--> The garden which is full of floewrs is watered every morning.

3) The dog is sitting on the chair. It is wild.

--> The dog that is wild is sitting on the chair.

4) The book is lying on the bookshelf. It is about geography.

--> The book which is about geography is lying on the bookshelf.

5) The computer is breaking down. It is an old one.

--> The computer which is an old one is breaking down.

6) The flowers are grown in this garden. They are fresh.

--> The flowers which are fresh are grown in this garden.

7) The sofa is put in the living room. It is new.

--> The sofa which is new is put in the living room.

8) The man holding a bunch of flowers. The man is my best friend.

--> The man who is my best friend holding a binch of flowers.

đề là j z

đề là j z